Process for the removal of phenols in a pure state from tars or tar oils



Patented Nov. 14 1933 "STATE TAR, I

Jenii Ksrpeu andM6ricGyiirgvfliibschp No= Drawing- Budapest, HungaryApplication December Serial No. 240,924, andin-Hungary. ra iaryis;

It has already been attempted'to remove the phenols from tars and torecover them'atthe same time in a pure state; 'Some success has beenattained by theaid of" chemicals but the processes concerned have notbeen of anypractical importancesince the cost of the chemicals required,which can only be recovered in part, was excessive. Y

Physical purification processes have also alreadybeen'proposed.Thusattempts have been made to utilize for'this purpose'that knownproperty'of concentrated'ethyl alcoholyby virtue of which thislatterfleifectiveli dissolves-the acid constituents of the tar,particularlythe phenols,

while hardly dissolving the hydrocarbons. pSatisfactory results could'not,however,"be obtained in this mannereither, since on the one hand aconsiderable content of phenol alwaysremained fin the'tar-hydrocarbonsthus treated, and on the other hand the alcoholic phenol solutionrecovered contained considerable quantities, about '20 to'25%, ofhydrocarbons, thus necessitating a'further chemical purificationl V Ithas further been proposed to extract the phenols from the tar by; meansof superheated P water. Under a pressure of about 40 atmospheres and ata temperature of about 225 success has in fact been obtained inproducing very good qualitative results, but this process is entirelyexcluded from industrial applicability on account of the difiicultiesincurred in the application of very high pressures and high temperaturesas well as the high costs of erection and maintenance.

. According to the present invention, the raw material, tar, tar, oilsor other tar derivatives, is treated under a moderate superatmosphericpressure and at a comparatively low temperature with a solvent forphenols diluted with water.

It is found, for instance, that if the raw material from which phenolsare to be removed is intimately mixed under moderate super-pressure, forexample 1.5-6 atmospheres, and at relatively low temperature, as forexample at 90-150, with a diluted aqueous solution'of a solvent ofphenols, as, for example, with methyl-, ethylor propyl alcohol, acetone,formaldehyde or acetaldehyde and the like, and the mixture. is then leftalone for a short time with maintenance of the temperature and pressure,then the contents of the reaction vessel separate into two layersofwhich one contains the tar hydrocarbons and the other the phenolsdissolved out of the tar by the aqueous solvent. If now the aqueoussolvent layer containing'the phenols is drawn off and cooled it dividesagain into two, layers, an under layer consisting of pure phenols and anupperlayer of hydrocarbons;

which contains the aqueous solvent, Thereupon the solvent is transferredagain to the tar from which the phenols are required to be removed andthe process is continued until the tar remaining in the reaction vesselcontains only oils which are neutral; 1. e. which consist exclusivelyResearches show that theaqueous solvent; for

example 20% alcohol, dissolves firstly the phenols ofthe strongest andthen successively those of less strong acid actionso that theseparation'of the individualphenols is possible in: the course of the-extractionand the applicationof a special fra'ctionating' process is therefore notnecessary.

Any suitable solvent which on the one hand dissolves phenols better thanhydrocarbons and f which on the other'hand is also soluble in water canbe applied. The-solvent essentially aids the sodium-sulphate and thelike, can'be added whereby as isshownbyiexperiment the degree of purityof the extracted phenols, clearly on 'account of the reduction of theamount of solution of the hydrocarbons, is increased.

The process results on the one hand in the recovery of pure phenols andon the other hand in V the complete freedom of the tar from the phenols.

The values of the pressure and the temperature are closely related tothe selected concentration of the aqueous solvent; if a very dilutesolvent is employed, pressure and temperature must be increased andconversely. on economic grounds it appears naturally to be indicated toemploy limits of pressure and temperature at which spe-' cial apparatusis unnecessary, the more so since it is an essential advantage of theinvention that no excessively high pressure or temperature is necessary.I

The process can, for example, be efiectedin the following manner:-

An autoclave suitably heated and provided with stirring apparatus inhalf filled with the tar from which the phenols are to be removed andhalf filled with 20% aqueous methyl alcohol. The heating is so regulatedthat a pressure of 6 atmospheres and a temperature of about 145continuously prevail in the autoclave. After stirringfor half an hourthe 'separated aqueous methyl alcohol-phenol solution is, withmaintenance of the pressure, transferred to a cooler connected to theautoclave; The cooler connected by a pipe to a collecting flask, as, forexample, a Florence flask, in which the contents of the cooler. whichiii are still under pressure are drawn off. The liquid on settlingseparates in the collecting vessel into an underlayer consisting ofphenols and an upper aqueous methyl alcohol layer. The latter is pumpedback into the autoclave and'the phenols are led 01f separately infractions or together.

Theprocess can also be effected in a continuous manner, as, for example,with the application of several autoclaves and coolers which case on theone hand the tar and on the other hand the aqueous solvent aremaintained in uninterrupted circulation. Instead of employing stirringthe two liquids can be introduced from opposite directions and alsoatomizers, heat exchangers and the like, can be employed. Since furtherthe system can be constructed entirely enclosed, losses of solvents arealmost completely avoidable. Mixtures of the aqueous solution ofdifferent solvents can also be employed.

What we claim and desire to secure by Letters into two layers consistingof phenols and aqueous solvent respectively, and then removing the phe--nols.

' 2. Processior removing phenols in a pure state from tars and tar oilsby treating said substances under a moderate superpressure not exceeding6 atmospheres and at a moderately elevated tem;-

perature of 90 to 150C. with an alcohol diluted with water, allowing themixture to stand until it separatesinto two layers, removing the aqueoussolvent layer which contains the dissolved phenols, causing the liquidof said layer by release of the pressure and cooling to separate intotwo layers consisting of phenols and aqueous solvent respectively, andthen removing the phenols.

3. Process for removing phenols in a pure state from tars and tar oilsby treating said substances under .a moderate superpressure notexceeding 6 atmospheres and at a temperature of 90 to 150 C. with anaqueous solution of a phenol solvent comprising about 20% alcohol andwater, allowing the mixture to stand until it separates into two layers,removing the aqueous solvent layer which contains the dissolved phenols,causing the liquid of said layer by release of the pressure and coolingto separate into two layers consisting of phenols and aqueous solventrespectively, and then removing the phenols.

4. Process for removing phenols in a pure state from tars and tar oilsby treating said substances under a moderate superpressure not exceeding6 atmospheres and at a temperature of 90 to 150 C. with an aqueoussolution of a phenol solvent in conjunction with a neutral mineral salt,allowing the mixture to stand until it separates into two layers,removing the aqueous solvent layer which contains the dissolved phenols,causing the liquid of said layer by release of the pressure and coolingto separate into two layers consisting of phenols and aqueous solventrespectively, and then removing the phenols.

5. Continuous process for removing phenols from tars and tar oils andsimultaneous recovery of the phenols in a substantially pure state by-treating said substances under a superpressure not exceeding 6atmospheres and at an elevates. temperature of 90 to 150 C. with anaqueous solution of a phenol solvent, allowing the mixture to separateinto two layers, removing the aqueous solvent layer which contains thedissolved phenols and causing it by release of the pressure and coolingto separate into two layers of phenols and aqueous solvent respectively,removing the phenols, and returning the aqueous solvent to the rawmaterial to be-cleaned.

JENG KARPATI.

'MORIC GYGRGY HiiBscH.

